U.S. patent number 6,031,044 [Application Number 08/993,016] was granted by the patent office on 2000-02-29 for polyurthanes with covalently bonded photoinitiator units.
This patent grant is currently assigned to BASF Aktiengesellschaft. Invention is credited to Erich Beck, Nicolas Kokel, Harald Larbig, Klaus Menzel, Wolfgang Reich, Guido Voit.
United States Patent |
6,031,044 |
Kokel , et al. |
February 29, 2000 |
Polyurthanes with covalently bonded photoinitiator units
Abstract
A polyurethane which is substantially self-dispersible in water
and is obtainable by reacting a) at least one polyisocyanate with
b) at least one polyol and c) at least one photoinitiator of the
general formula I ##STR1## where R is a radical of the formula II
##STR2## or is --CR.sup.7 R.sup.8 R.sup.9,
P(.dbd.O)(R.sup.10).sub.2 or SO.sub.2 R.sup.11, the number-average
molecular weight M.sub.n of the polyurethane being greater than
2700, and its use. The invention also relates to aqueous
polyurethane resin dispersions and coating compositions comprising
the novel polyurethanes, and to their use.
Inventors: |
Kokel; Nicolas (Ludwigshafen,
DE), Larbig; Harald (Ludwigshafen, DE),
Menzel; Klaus (Ludwigshafen, DE), Beck; Erich
(Ladenburg, DE), Reich; Wolfgang (Maxdorf,
DE), Voit; Guido (Schriesheim, DE) |
Assignee: |
BASF Aktiengesellschaft
(Ludwigshafen, DE)
|
Family
ID: |
7815462 |
Appl.
No.: |
08/993,016 |
Filed: |
December 18, 1997 |
Foreign Application Priority Data
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Dec 19, 1996 [DE] |
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196 53 183 |
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Current U.S.
Class: |
524/839;
427/372.2; 427/385.5; 427/487; 522/35; 522/38; 428/423.1; 427/520;
427/508; 522/39; 522/90; 522/96; 522/97; 525/455; 525/123; 524/840;
524/507; 524/591; 522/904; 522/905 |
Current CPC
Class: |
C08G
18/2805 (20130101); C08G 18/30 (20130101); C08G
18/675 (20130101); C08G 18/0804 (20130101); C08G
18/672 (20130101); Y10S 522/905 (20130101); Y10T
428/31551 (20150401); Y10S 522/904 (20130101) |
Current International
Class: |
C08G
18/30 (20060101); C08G 18/00 (20060101); C08G
18/08 (20060101); C08G 18/67 (20060101); C08G
18/28 (20060101); C08J 003/00 (); C08K 003/20 ();
C08L 075/00 (); C08F 002/46 () |
Field of
Search: |
;428/423.1
;524/591,839,840,507 ;427/487,508,520,372.2,385.5
;522/35,38,39,90,96,97 ;525/123,455 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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30 05 034 |
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Aug 1981 |
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DE |
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37 38 567 A1 |
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Sep 1988 |
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DE |
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39 11 827 A1 |
|
Oct 1990 |
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DE |
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40 31 732 A1 |
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Apr 1992 |
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DE |
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42 03 546 |
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Aug 1993 |
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DE |
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WO 96/08524 |
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Mar 1996 |
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WO |
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Primary Examiner: Niland; Patrick D.
Attorney, Agent or Firm: Oblon, Spivak McClelland, Maier
& Neustadt, P.C.
Claims
We claim:
1. A polyurethane which is substantially self-dispersible in water
and has a number-average molecular weight M.sub.n of more than
2700, which is obtained by reacting
a) at least one polyisocyanate with
b) at least one polyol consisting of
b1) from 9 to 100 mol-% of a polyol or a mixture of two or more
polyols having a molecular weight of at least 500 and
b2) from 0 to 91 mol-% of a polyol or a mixture of two or more
polyols having a molecular weight of less than 500,
b1) and b2) together making up 100 mol-% of component b), and
c) at least one photoinitiator of the formula I ##STR6## where R is
a radical of the formula II ##STR7## or is --CR.sup.7 R.sup.8
R.sup.9, P(.dbd.O)(R.sup.10).sub.2 or SO.sub.2 R.sup.11
and at least one of the radicals R.sup.1, R.sup.2, R.sup.5,
R.sup.6, and R.sup.9 is used for incorporation into the
polyurethane and the remaining radicals, one or more of the
R.sup.1, R.sup.2, R.sup.5, R.sup.6, and R.sup.9,
each independently are hydrogen, C.sub.1-12 -alkyl, C.sub.1-12
-alkoxy, halogen, cyano, nitro or sulfo,
R.sup.3 and R.sup.4 each independently are hydrogen or COOH or
together are S,
R.sup.7 and R.sup.8 each independently are hydrogen, C.sub.1-12
-alkyl, C.sub.1-12 -alkenyl, C.sub.1-12 -alkoxy or phenyl or
together are .dbd.O or C.sub.2-6 -alkylene, R.sup.9 is OR.sup.11,
N(R.sup.11).sub.2, N-piperidyl, N-piperazyl or N-morpholino,
R.sup.10 is C.sub.1-12 -alkyl, C.sub.1-12 -alkanoyl, phenyl or
benzoyl, each of which can in turn be substituted by halogen,
C.sub.1-12 -alkyl or C.sub.1-12 -alkoxy, R.sup.11,
independently at each occurrence, is hydrogen is unsubstituted or
OH--, NHR.sup.10 --, NH.sub.2 -- or SH-substituted C.sub.1-6
-alkyl, C.sub.1-12 -alkoxy or phenyl, or together are C.sub.2-5
-alkylene, and,
if R.sup.9 is OR.sup.11 and R.sup.11 is hydrogen, R.sup.7 and
R.sup.8 in combination cannot be hydrogen and phenyl;
wherein said polyol b1) is selected from the group consisting of a
polyester polyol, a polycarbonate diol, a lactone polyester diol
and a polyether diol; wherein said polyester polyol is formed by
reacting an alcohol with a polycarboxylic acid; and wherein said
polycarboxylic acid is represented by the formula:
HOOC--(CH.sub.2)Y--COOH; and
wherein said polyol b2) is selected from the group consisting of an
alcohol of formula HO--(CH.sub.2)13 OH, where x is 1 to 20,
neopentyl glycol, a bis(hydroxymethyl)cyclohexane,
2-methyl-1,3-propanediol, methylpentanediol, diethyl glycol,
triethyl glycol, tetraethyl glycol, polyethylene glycol,
dipropylene glycol, polypropylene glycol, dibutylene glycol and
polybutylene glycol.
2. A polyurethane as claimed in claim 1, wherein during the
reaction there is additionally a component or a mixture of two or
more components selected from
d) a polyamine or a mixture of two or more polyamines,
e) a compound or a mixture of two or more compounds having at least
one isocyanate-reactive group and at least one group which is
ionizable by addition of base or acid or by quatermization,
f) a compound or a mixture of two or more compounds having at least
one isocyanate-reactive group and at least one olefinically
unsaturated double bond.
3. A process for preparing a polyurethane which is substantially
self-dispersible in water, wherein at least,
a) polyisocyanates are reacted with
b) polyols, and
c) photoinitiators of the formula I ##STR8## in which b) and c) are
as defined in claim 1, in such a way that the number-average
molecular weight M.sub.n of the polyurethane is more than 2700.
4. An aqueous polyurethane dispersion, which comprises at least one
polyurethane which is substantially self-dispersible in water and
has a number-average molecular weight M.sub.n of more than 2700 and
is obtained by reacting
a) polyisocyanates with
b) polyols, and
c) photoinitiators of the formula I ##STR9## in which b) and c) are
as defined in claim 1.
5. An aqueous polyurethane dispersion as claimed in claim 4,
wherein during the reaction a component or a mixture of two or more
components is present which are selected from
d) a polyamine or a mixture of two or more polyamines,
e) a compound or a mixture of two or more compounds having at least
one isocyanate-reactive group and at least one group which is
ionizable by addition of base or acid or by quatemization,
f) a compound or a mixture of two or more compounds having at least
one isocyanate-reactive group and at least one olefinically
unsaturated double bond.
6. A process for preparing an aqueous polyurethane dispersion,
which comprises reacting at least
a) polyisocyanates with
b) polyols, and
c) photoinitiators of the formula I ##STR10## in which b) and c)
are as defined in claim 1, with one another and dispersing the
product in water.
7. A Process according to claim 6, characterized in that the
product is dispersed in water after neutralization.
8. A coating composition obtained by dissolving or dispersing in
water at least one polyurethane as claimed in claim 1 together with
further polymeric binders and further customary coatings
additives.
9. A coating composition obtained by dissolving or dispersing in
water at least one polyurethane as claimed in claim 2 together with
further polymeric binders and further customary coatings
additives.
10. A coating composition obtained by dissolving or dispersing in
water at least one polyurethane prepared as claimed in claim 3
together with further polymeric binders and further customary
coatings additives.
11. A coating composition obtained by dissolving or dispersing in
water at least one polyurethane prepared as claimed in claim 4
together with further polymeric binders and further customary
coatings additives.
12. A process for preparing a coating composition, which comprises
dissolving or dispersing in water at least one polyurethane as
claimed in claim 1 together with further polymeric binders and
further customary coatings additives.
13. A process for preparing a coating composition, which comprises
dissolving or dispersing in water at least one polyurethane as
claimed in claim 2 together with further polymeric binders and
further customary coatings additives.
14. A process for preparing a coating composition, which comprises
dissolving or dispersing in water at least one polyurethane
prepared as claimed in claim 3 together with further polymeric
binders and further customary coatings additives.
15. A process for preparing a coating composition, which comprises
dissolving or dispersing in water at least one polyurethane
prepared as claimed in claim 4 together with further polymeric
binders and further customary coatings additives.
16. A process for coating articles, which comprises applying to the
article a coating composition as claimed in claim 7 by means of a
technique which is customary in coatings technology, first drying
said applied composition and then crosslinking it by irradiation
with UV rays.
17. A process for coating articles, which comprises applying to the
article a coating composition prepared as claimed in claim 8 by
means of a technique which is customary in coatings technology,
first drying said applied composition and then crosslinking it by
irradiation with UV rays.
18. An article coated with an aqueous polyurethane dispersion as
claimed in claim 4.
19. An article coated with an aqueous polyurethane dispersion as
claimed in claim 5.
20. An article coated with an aqueous polyurethane dispersion
prepared as claimed in claim 6.
21. An article coated with a coating composition prepared as
claimed in claim 7.
22. An article coated with a coating composition prepared by means
of a process as claimed in claim 8.
23. An article coated by means of a process as claimed in claim 9.
Description
The invention relates to a water-soluble and/or water-dispersible
polyurethane (PU) having photoinitiator units bonded covalently to
the PU chain, to a process for preparing such a polyurethane, to
aqueous solutions and/or dispersions comprising such a
polyurethane, and to a process for preparing such an aqueous
polyurethane dispersion.
Aqueous dispersions of polyurethanes are known (see for example D.
G. Oertel "Kunststoff Handbuch 7", 2nd Edition, Carl Hanser Verlag
Munich/Vienna, pp. 24 to 25 and pp. 571 to 574. These
water-dispersed polyurethanes are used as binders (also referred to
below as PU binders) in, for example, coating compositions for
painting, printing, bonding or otherwise coating substrates. The
coatings obtainable in this way usually show a favorable
combination of properties in respect of adhesion, abrasion
resistance, low-temperature flexibility, toughness and gloss.
For the purposes of the invention the term coating compositions
refers to ready-to-use dispersions of the PU binders in question,
together if appropriate with further additives. A coating for the
purposes of the invention is either a surface-sealing layer
(generally a coat) or an adhesive bond, unless specified otherwise.
Therefore, an aqueous polyurethane dispersion can be either the
aqueous dispersion of the PU binders or (if the dispersion is ready
to use to prepare a coating without the addition of further
additives) a coating composition in the above sense.
A further advantage of the aqueous polyurethane dispersions lies in
the substantial absence of organic solvents, which makes them
ecologically advantageous alternatives to known, solvent-containing
coating or adhesive systems.
A disadvantage of the PU binders dispersed in aqueous solution is
the mandatory presence of emulsifiers or hydrophilicizing groups.
This greatly reduces the resistance of the coating or bond to, for
instance, water, solvents, acids, alkalis, surfactants or other
household chemicals. Long-term action of the abovementioned
chemicals on a coating leads at least to a reduction in its quality
and possibly even to its complete destruction.
In order to solve this problem the attempt has been made to render
aqueous polyurethane dispersions of PU binders having
radiation-crosslinkable groups (in general, olefinically
unsaturated double bonds) UV-crosslinkable by the addition of low
molecular mass photoinitiators.
Thus DE-A1 30 05 034 describes the preparation of coatings on
electrically conductive articles, where the PU binder contains
olefinically unsaturated double bonds. To crosslink the
polyurethane dispersion, a low molecular mass photoinitiator is
added which is stirred into the dispersion.
DE-A1 39 11 827 likewise describes aqueous polyurethane dispersions
where the PU binder contains olefinically unsaturated double bonds.
For crosslinking the dispersion by UV radiation, a low molecular
mass photoinitiator is added.
DE-A1 40 31 732 and DE-A1 42 03 546 again relate to
radiation-curable PU binders where in each document a low molecular
mass photoinitiator is added to the aqueous polyurethane
dispersion.
A disadvantage of all of the techniques disclosed is that the
photoinitiator and/or, if appropriate, fragmentation residues
thereof are not bound in the binder matrix in such a way as to be
stable to diffusion after crosslinking by UV radiation. In some
circumstances, these low molecular mass constituents can diffuse to
the surface of the coating. Such fragmentation products often give
the coating an unpleasant odor. In some cases the fragmentation
products can even be toxic. Also disadvantageous is the softening
effect of such low molecular mass additives on the mechanical
properties of the coating.
A further serious disadvantage arising from the addition of low
molecular mass photoinitiators for crosslinking the olefinically
unsaturated double bonds of the polyurethanes lies in the deficient
recyclability of the coating compositions by, for example, the ever
more frequently employed technique of ultrafiltration.
In this technique, the overspray is washed out with water from the
exhaust air from a spraybooth and the resulting water, enriched
with coating composition, is subjected to ultrafiltration until the
composition of the aqueous dispersion corresponds again to the
coating composition employed originally.
With this technique, however, all constituents of the original
coating composition which fall below a certain molecular weight
accummulate in the circulation water and are therefore removed from
the coating composition. This process also affects the low
molecular mass photoinitiators employed to date. As a result of the
continuous associated decrease in the concentration of low
molecular mass photoinitiator in the coating composition, as the
period of ultrafiltration progresses there is a markedly reduced
reactivity in the applied coating in terms of crosslinking by
irradiation. This loss of reactivity can in general only be
countered by subsequently adding more photoinitiator.
The radiation-curable, polyurethane-based coating compositions
known from the prior art are therefore unable, or not sufficiently
able, to meet the heightened performance expectations.
The prior art has also disclosed polyurethanes which may comprise
photoinitiators as a constituent bonded covalently to the
polyurethane chain.
WO 96/08524, although disclosing sidechain-functionalized aqueous
polyurethane dispersions whose functionalization can comprise
photoinitiators, does not disclose any photoinitiators suitable for
incorporation into the polyurethane. Moreover, functionalization
takes place by way of carbodiimide groups, which necessitates a
laborious synthesis prior to incorporation into the
polyurethane.
DE-A1 37 38 567 discloses a polyurethane mixture in which a
photoinitiator capable of reaction with polyurethanes is added to
the polyisocyanates before the thermal polyaddition reaction.
However, no aqueous PU binders are described, and the system is
irradiated prior to thermal aftercuring.
The prior art therefore discloses no water-soluble or
water-dispersible polyurethane binders which comprise covalently
bonded photoinitiators and can be prepared, simply, using known
methods of polyurethane synthesis.
It is an object of the present invention, therefore, to provide PU
binders comprising photoinitiators incorporated covalently in the
binder. The PU binders should, from aqueous solutions or
dispersions and by thermal drying alone, lead to tack-free,
mechanically stable coatings and should be photochemically
crosslinkable by irradiation at any subsequent point in time.
We have found that this object is achieved by a polyurethane which
is substantially self-dispersible in water and has a number-average
molecular weight M.sub.n of more than 2700, which is attainable by
reacting
a) at least one polyisocyanate with
b) at least one polyol consisting of
b1) from 9 to 100 mol-% of a polyol or of a mixture of two or more
polyols having a molecular weight of at least 500 and
b2) from 0 to 91 mol-% of a polyol or of a mixture of two or more
polyols having a molecular weight of less than 500,
b1) and b2) together making up 100 mol-% of component b), and
c) at least one photoinitiator of the formula I ##STR3## where R is
a radical of the formula II ##STR4## or is --CR.sup.7 R.sup.8
R.sup.9, P(.dbd.O)(R.sup.10).sub.2 or SO.sub.2 R.sup.11
and at least one of the radicals R.sup.1, R.sup.2, R.sup.5, R.sup.6
and R.sup.9 is used for incorporation into the polyurethane
and the remaining radicals, one or more of R.sup.1, R.sup.2,
R.sup.5, R.sup.6 and R.sup.9, each independently are hydrogen,
C.sub.1-12 -alkyl, C.sub.1-2 -alkoxy, halogen, cyano, nitro or
sulfo,
R.sup.3 and R.sup.4 each independently are hydrogen or COOH or
together are S,
R.sup.7 and R.sup.8 each independently are hydrogen, C.sub.1-12
-alkyl, C.sub.1-12 -alkenyl, C.sub.1-12 -alkoxy or phenyl or
together are .dbd.O or C.sub.2-6 -alkylene,
R.sup.9 is OR.sup.11, N(R.sup.11).sub.2, N-piperidyl, N-piperazyl
or N-morpholino,
R.sup.10 is C.sub.1-12 -alkyl, C.sub.1-12 -alkanoyl, phenyl or
benzoyl, each of which can in turn be substituted by halogen,
C.sub.1-12 -alkyl or C.sub.1-12 -alkoxy,
R.sup.11, independently at each occurrence, is hydrogen or is
unsubstituted or OH--, NHR.sup.10 --, NH.sub.2 -- or SH-substituted
C.sub.1-6 -alkyl, C.sub.1-12 -alkoxy or phenyl, or together are
C.sub.2-5 -alkylene,
(and, if R.sup.9 is OR.sup.11 and R.sup.11 is hydrogen, R.sup.7 and
R.sup.8 in combination cannot be hydrogen and phenyl.
If desired, one or more of the following components may be present
during the reaction:
d) a polyamine or a mixture of two or more polyamines,
e) a compound or a mixture of two or more compounds having at least
one isocyanate-reactive group and at least one group which is
ionizable by addition of base or acid or by quaternization,
f) a compound or a mixture of two or more compounds having at least
one isocyanate-reactive group and at least one olefinically
unsaturated double bond.
The term polyurethane essentially self-dispersible in water refers
for the purposes of the invention to a polyurethane which can be
dispersed stably in water merely by adding a small amount, if any,
of dispersing aids. The novel polyurethanes require addition of
dispersing aids in an amount of at most about 5% by weight,
preferably less than 3% by weight and, with particular preference,
less than 1% by weight, based on the solids content of the
dispersion and, in particular, on the mass of the PU binders in the
dispersion.
For the purposes of the present invention the term drying refers to
the reduction in the solvent content of the coating until a
tack-free, mechanically stable surface is obtained, the term
solvent referring both to organic solvents and water as continuous
phase.
Organic solvents can be present in the novel polyurethane
dispersions in minor amounts, for example in an amount of not more
than about 10% by weight, preferably less than about 7% by weight
and, with particular preference, less than about 5% by weight,
based on the overall dispersion.
As component a) for preparing the novel polyurethanes, the
polyisocyanates commonly employed in polyurethane chemistry are
suitable.
Those which can be mentioned in particular are diisocyanates
X(NCO).sub.2 where X is an aliphatic hydrocarbon radical of 4 to 12
carbons, a cycloaliphatic or aromatic hydrocarbon radical of six to
fifteen carbons or an araliphatic hydrocarbon radical of seven to
fifteen carbon. Examples of such dilsocyanates are tetramethylene
diisocyanate, hexamethylene diisocyanate (HDI), dodecamethylene
diisocyanate, 1,4-diisocyanatocyclohexane,
1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (IPDI),
2,2-bis-(4-isocyanatocyclohexyl)propane, trimethyihexane
diisocyanate, 1,4-diisocyanatobenzene, 2,4-diisocyanatotoluene,
2,6-diisocyanatotoluene, 4,4'-diisocyanatodiphenylmethane,
tetramethylxylylene diisocyanate, 2,4'-diisocyanatodiphenylmethane,
p-xylylene diisocyanate, the isomers of
bis(4-isocyanatocyclohexyl)methane, such as the trans/trans, the
cis/cis and the cis/trans isomer, and mixtures of these
compounds.
Particularly important mixtures of these isocyanates are the
mixtures of the respective structural isomers of
diisocyanatotoluene and diisocyanatodiphenylmethane; the mixture
comprising 80 mol-% 2,4-diisocyanatotoluene and 20 mol-%
2,6-diisocyanatotoluene is particularly suitable. Also of
particular advantage are the mixtures of aromatic isocyanates, such
as 2,4-diisocyanatotoluene or 2,6-diisocyanatotoluene or a mixture
of both, with aliphatic or cycloaliphatic isocyanates, such as HDI
or IPDI, the preferred ratio of aliphatic to aromatic isocyanates
being from about 4:1 to 1:4.
As component a) it is also possible to employ isocyanates which in
addition to the free isocyanate groups carry further capped
isocyanate groups, for example urethane groups.
If desired it is also possible to use those isocyanates which carry
only one isocyanate group. In general the proportion of such
isocyanates is not more than 10 mol-%, based on the overall molar
amount of the monomers. The monoisocyanates may carry further
functional groups, such as olefinically unsaturated groups or
carbonyl groups, in which case they serve to introduce these
functional groups into the polyurethane. They may enhance the
dispersing or crosslinking or other polymer-analogous reactions of
the polyurethane or may even make such operations or reactions
possible. Examples of suitable such compounds are those such as
isopropenyl .alpha.,.alpha.-dimethylbenzyl isocyanate (TMI).
In order to prepare polyurethanes having a certain degree of
branching or of crosslinking it is possible, for example, to employ
isocyanates having a functionality of three or more. Such
isocyanates are obtained, for example, by reacting difunctional
isocyanates with one another in such a way that some of their
isocyanate groups are derivatized to form allophanate, biuret or
isocyanurate groups. Examples of customary commercial compounds are
the isocyanurate and the biuret of hexamethylene diisocyanate.
Examples of other suitable polyisocyanates of higher functionality
are those that have urethane groups and are based on 2,4- or
2,6-diisocyanatotoluene or a mixture of both, IPDI, tetramethylene
diisocyanate or hexamethylene diisocyanate on the one hand and on
low molecular mass polyhydroxy compounds such as trimethylolpropane
on the other.
In view of the processability of the polyurethanes, the proportion
of trifunctional or higher polyfunctional polyisocyanates should be
restricted. Thus their proportion should be limited to about 50% by
weight, preferably less than about 35% by weight and, with
particular preference, less than about 25% by weight.
Suitable components b) are polyols of relatively high molecular
mass, preferably diols, which have a molecular weight of more than
500, for example from about 500 to 5000, preferably from about 1000
to 3000 g/mol. These polyols are referred to below as polyols b1)
and are primarily responsible for good film formation and
elasticity.
The polyols of component b1) are, in particular, polyester polyols
known, for example, from Ullmanns Encyklopadie der technischen
Chemie, 4th ed., vol. 19, pp. 62-65. Preference is given to the use
of polyester-polyols which are obtained by reacting dihydric
alcohols with polycarboxylic acids (preferably dibasic carboxylic
acids). In place of the free polycarboxylic acids it is also
possible to use the corresponding polycarboxylic anhydrides or
corresponding polycarboxylic esters of lower alcohols, or mixtures
thereof, to prepare the polyesterpolyols. The polycarboxylic acids,
their esters and anhydrides are also referred to below as component
b1.1). The polycarboxylic acids may be aliphatic, cycloaliphatic,
araliphatic, aromatic or heterocyclic and may be unsubstituted or
substituted, for example by halogens, and/or unsaturated. Examples
of such compounds are suberic, azelaic, phthalic, isophthalic and
terephthalic acid, phthalic, tetrahydrophthalic, hexahydrophthalic,
tetrachlorophthalic, endomethylenetetrahydrophthalic and glutaric
anhydride, maleic acid, maleic anhydride, fumaric acid or dimeric
fatty acids. The polycarboxylic acids specified can be employed
either as exclusive acid component or in a mixture with one another
to synthesize component b1). Preference is given to the carboxylic
acids of the formula HOOC--(CH.sub.2).sub.y --COOH, where y is
1-20, preferably 2-20, examples being succinic, adipic,
dodecanedicarboxylic and sebacic acid. In place of the free
polycarboxylic acids it is possible, where feasible, also to use as
component b1.1) the corresponding polycarboxylic anhydrides or
corresponding polycarboxylic esters of lower alcohols, or mixtures
thereof, to prepare the polyesterpolyols.
Examples of suitable polyhydric, preferably dihydric, alcohols as
component b1.2) for reaction with the polycarboxylic acid component
to synthesize component b1) are ethylene glycol, 1,2-propanediol,
1,3-propanediol, 1,3-butanediol, 1,4butenediol, 1,4butynediol,
1,5-pentanediol, 1,6-hexanediol, neopentylglycol,
bis(hydroxymethyl)cyclohexanes, such as
1,4-bis(hydroxymethyl)cyclohexane, 2-methyl-1,3-propanediol,
methylpentanediols, and also diethylene glycol, triethylene glycol,
tetraethylene glycol, polyethylene glycol, dipropylene glycol,
polypropylene glycols, dibutylene glycol and polybutylene glycols.
Preference is given to neopentylglycol and to alcohols of the
formula HO--(CH.sub.2).sub.x --OH, where x is 1-20, preferably
2-20, examples being ethylene glycol, 1,4-butanediol,
1,6-hexanediol, 1,8-octanediol and 1,12-dodecanediol.
Also suitable, furthermore, are polycarbonatediols as can be
obtained, for example, by reacting phosgene with an excess of the
low molecular mass alcohols (b1.2)) mentioned as structural
components for the polyester-polyols.
Lactone-based polyesterdiols are also suitable as component b1),
these being homopolymers or copolymers of lactones; preferably
adducts, containing terminal hydroxyl, of lactones with suitable
difunctional starter molecules. Preferred lactones are those
derived from compounds of the formula HO--(CH.sub.2).sub.z --COOH,
where z is 1-20. Examples are .epsilon.-caprolactone,
.beta.-propiolactone, .gamma.-butyrolactone and/or
methyl-.epsilon.-caprolactone and mixtures thereof. Examples of
suitable starter components are the low molecular mass diols
mentioned above as structural components for the polyesterpolyols.
The corresponding polymers of .epsilon.-caprolactone are
particularly preferred. Lower polyesterdiols or polyetherdiols can
also be employed as starters for preparing the lactone polymers.
Instead of the polymers of lactones it is also possible to employ
the corresponding, chemically equivalent polycondensates of the
hydroxycarboxylic acids corresponding to the lactones.
The polyesterpolyols can also be synthesized from minor amounts of
monofunctional or higher polyfunctional monomers or a mixture of
both.
Other suitable monomers b1) are polyetherdiols. They are obtainable
in particular by polymerizing ethylene oxide, propylene oxide,
butylene oxide, tetrahydrofuran, styrene oxide or epichlorohydrin
with itself, for example in the presence of BF.sub.3, or by
carrying out addition reactions of these compounds, individually,
as a mixture or in succession, with starter components containing
reactive hydrogens, such as water, alcohols or amines, for example
ethylene glycol, 1,2-propanediol, 1,3-propanediol, 2,2-bis
(4-hydroxydiphenyl)propane or aniline. Particular preference is
given to polytetrahydrofuran having a molecular weight from about
500 to about 4000, preferably from about 500 to about 3000.
Both when preparing the polyesterpolyols and when preparing the
polyetherpolyols it is possible to employ alcohols having a
functionality of more than two in minor amounts as component b1.3).
Particular examples of such compounds are trimethylolpropane,
pentaerytritol, glycerol, sugars, for example glucose, oligomerized
polyols, for example dimeric or trimeric ethers of
trimethylolpropane, glycerol or pentaerythritol. The above
compounds are likewise suitable as starter components for
synthesizing the polyetherpolyols.
The polyol compounds having a functionality >2 are preferably
used only in minor amounts for synthesizing the polyesterpolyols
and/or polyetherpolyols.
Likewise suitable as component b1) are polyhydroxyolefins,
preferably those having two terminal hydroxyls, for example
.alpha.,.omega.-dihydroxypolybutadiene,
.alpha.,.omega.-dihydroxypolymethacrylates or
.alpha.,.omega.-dihydroxypolyacrylates.
The polyols listed under component b1) can also be employed in the
form of mixtures of two or more thereof in any desired
proportions.
The hardness and modulus of elasticity of the polyurethanes can in
general be increased if the polyols b2) include not only the
polyols b1) but also low molecular mass diols or polyols,
preferably diols, b2) having a molecular weight of less than about
500, preferably from 62 to about 500 and, with particular
preference, from 62 to about 200 g/mol.
As component b2) use is made in particular of the short-chain
alkanediols referred to as component b1.2), preference being given
to neopentylglycol and to unbranched diols having 2 to 12 C atoms
and an even number of C atoms, examples being ethylene glycol,
1,4butanediol or 1,6-hexanediol. If desired, component b2) can also
include, in minor amounts, alcohols having a higher functionality
with respect to isocyanates, as have been described, for example,
as component b1.3).
The components b1) and b2) described for synthesizing the novel
polyurethanes can also be employed as mixtures of b1) and b2) for
the purposes of the invention. In this case the proportion of the
polyols b1), based on the overall amount of polyols b1) plus b2),
is from 9 to 100 mol-% and the proportion of the polyols b2), based
on the overall amount of polyols b1) plus b2), is from 0 to 91
mol-%. The ratio of the polyols b2) to the polyols b1) is
preferably from 10:1 to 0:1, with particular preference from 8:1 to
0:1.
Component c) used to prepare the novel polyurethane comprises
photoinitiators of the formula I whose radicals have already been
defined above.
The compounds of the formula I carry at least one functional group
which, possibly in its derivatized form, serves to incorporate the
photoinitiator into the polyurethane. All functional groups which
enable such incorporation to take place are suitable for use in the
context of the present invention. Particular such groups are either
isocyanate groups or functional groups that carry an acidic
hydrogen which can be determined by the Zerewittinoff Test,
examples being hydroxyl, mercaptan, primary or secondary amino or
carboxyl groups.
In addition to the abovementioned groups the radicals R.sup.1,
R.sup.2, R.sup.5, R.sup.6 and/or R.sup.9 can also be radicals of
structure A-X where X is a functional group which serves for
incorporation into the polyurethane and A is C.sub.1-12 -alkyl or
an alkanoyl, aryl or aryloxy radical.
Components c) of the formula I contain from 1 to 4, preferably from
I to 3 and, with particular preference, 1 or 2 radicals R.sup.1,
R.sup.2, R.sup.5, R.sup.6 or R.sup.9 which have a functional group
serving for incorporation into the poly-urethane.
Where R is a phenyl ring which is unsubstituted or substituted by
R.sup.4, R.sup.5 and R.sup.6, the resulting photoinitiators are of
the benzophenone series. Where R.sup.3 and R.sup.4 together then
form a sulfide bridge between the phenyl rings, the resulting
photoinitiators are thioxanthones.
If R is the group --CR.sup.7 R.sup.8 R.sup.9 then the resulting
photoinitiator basic structures, in accordance with the above
definitions of R.sup.7, R.sup.8 and R.sup.9, are those of the
benzoin ethers and acyloin ethers, of the benzil ketals and
dialkoxyacetophenones, of the hydroxy- and aminoalkylphenones and
of the .alpha.-sulfonyl ketones.
If R is --C(.dbd.O)R.sup.9, then in accordance with the above
definition of R.sup.9 the resulting low molecular mass
photoinitiators are those of the phenylglyoxylic ester or
phenylglyoxylic amide series.
If R is --P(.dbd.O)(R.sup.10).sub.2 then the resulting
photoinitiators belong to the class of the acylphosphine
oxides.
The following compounds are particularly suitable for use as
component c) in the novel polyurethanes:
2-, 3-and 4-hydroxybenzophenone,
2-hydroxy-5-methylhydroxybenzophenone,
2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octyloxybenzophenone,
2-hydroxy-4-dodecyloxybenzophenone,
2-hydroxy-5-chlorohydroxybenzophenone,
2-hydroxy-4-methoxy-4'-methylbenzophenone,
2-hydroxy-4-methoxy-4'-chlorobenzophenone,
4-hydroxy-3-methylbenzo-phenone, 4-hydroxy-4'-methoxybenzophenone,
4-hydroxy-4'-chlorobenzophenone, 4-hydroxy-4'-fluorobenzophenone,
4-hydroxy-4'-cyanobenzophenone,
4-hydroxy-2',4'-dimethoxybenzophenone, 2,2',4,4'- and
2,4-dihydroxybenzophenone, 4-tert-butyl-2,4-dihydroxybenzophenone,
2,2'-dihydroxy-4-methoxybenzophenone,
2,2'-dihydroxy-4-octoxybenzophenone,
2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2,4,4'-, 2,3,4- and
2,4,6-trihydroxybenzophenone, 2,2,'-, 4,4'-, 2,3,4,4'- and
2,3',4,4'-tetrahydroxybenzophenone, 2-, 3- and 4-aminobenzophenone,
2-amino-4-methylbenzophenone, 2-amino-6methylbenzophenone,
2-amino-4'-methylbenzophenone,
2-amino-4'-chloro-5-fluorobenzophenone,
2-amino-5-chlorobenzophenone, 2-amino-5-bromobenzophenone,
2-amino-5-methylbenzophenone, 2-amino-N-ethylbenzophenone,
2-amino-2',5'-dimethylbenzophenone, 4amino-2-chlorobenzophenone,
4-amino-4'-methoxybenzophenone, 3,4-, 4,4'- and
3,3'-diaminobenzophenone, 4,4'-bis(methylamino)benzophenone,
3,3',4,4'-tetraaminobenzophenone, 2-, 3- and 4-benzoylbenzoic acid,
2-benzoyl-3'-methylbenzoic acid, 2-benzoyl-4'-ethylbenzoic acid,
2-benzoyl-3,6-dimethylbenzoic acid, 2-benzoyl-2',6'-dimethylbenzoic
acid, 2-benzoyl-3',4'-dimethylbenzoic acid,
2-benzoyl-2',4',6-dimethylbenzoic acid, 2-benzoyl-p-hydroxybenzoic
acid, 2-benzoyl-4'-methyl-3'-chlorobenzoic acid,
2-benzoyl-6-chlorobenzoic acid, 4-benzoyl-4'-isopropylbenzoic acid,
4-benzoyl-4'-chlorobenzoic acid,
4-benzoyl-4'-(2-carboxypropyl)benzoic acid, 2,4-, 3,4- and
4,4'-benzophenonedicarboxylic acid, 2',3,4-, 3,3',4- and
3,4,4'-benzophenonetricarboxylic acid,
3,3',4,4'-benzophenonetetracarboxylic acid and -tetracarboxylic
dianhydride, 2-hydroxy-4-methoxy-5-sulfobenzophenone,
4-(4-carboxyphenyloxy)benzophenone,
4-(3,4-bis(carboxy)phenyloxy)benzophenone and the corresponding
anhydride, 4'-(4-carboxyphenyloxy)benzophenone4carboxylic acid,
4'-(4-carboxyphenyloxy)benzophenone-3,4-dicarboxylic acid and the
corresponding anhydride,
4'-(3,4-bis(carboxy)phenyloxy)benzophenone-2,4- and
3,4-dicarboxylic acid and the corresponding anhydrides,
4-(4-cyanobenzoyl)thiophenol, 4(2-hydroxyethoxy)phenyl
2-hydroxy-2-propyl ketone, 4-(2-aminoethoxy)phenyl
2-hydroxy-2-propyl ketone, 4-(2-hydroxycarbonylmethoxy)phenyl
2-hydroxy-2-propyl ketone, 4-(2-isocyanatoethoxy)phenyl
2-hydroxy-2-propyl ketone, 4(2-isocyanatomethoxy)phenyl
2-hydroxy-2-propyl ketone,
2-([2-]6-isocyanatohexylaminocarbonyloxy)ethoxylthioxanthone,
phenylglyoxylic acid, esters of phenylglyoxylic acid with polyols,
the polyols which can be used being essentially the polyols
described under b1.2) and b1.3) and used for the polyurethane
synthesis, amides of phenylglyoxylic acid with amino alcohols, the
alcohols which can be employed as amino alcohols being monoamino
polyols having two aliphatically bonded hydroxyl groups, as
described in the present application under component d) in the
context of the polyurethane synthesis. Examples of monoamino
polyols having more than two aliphatically bonded hydroxyl groups
which are likewise suitable for preparing the amides of
phenylglyoxylic acid are tris(hydroxy-methyl)methylamine,
2-[tris(hydroxymethyl)methylamino]ethanesulfonic acid,
3-[tris(hydroxymethyl)methylamino]propanesulfonic acid,
N-[tris(hydroxymethyl)methyl]glycine,
tris(3-hydroxypropyl)methylamine, glucamine and
N-(2-hydroxyethyl)glucamine or the amino diols, such as
N,N'-bis(2-hydroxyethyl)ethylenediamine, and reaction products of a
primary polyether diamine and, per mole of polyether diamine, 2 mol
of ethylene oxide, propylene oxide and/or butylene oxide, the
conditions for the reaction of the polyether diamine with the
alkylene oxide being selected such that there is selective
formation of the N,N'-bis(hydroxyalkylamine) derivative having two
secondary amino groups. Examples of the polyether diamines are
4,7-dioxadecane-1,10-diamine, 4,11-dioxatetradecane-1,14-diamine,
.alpha.-(2-aminomethylethyl)-.omega.-(2-aminomethylethoxy)poly[oxy(methyl-
1,2-ethanediyl)] with a molecular weight of from about 200 to about
3000, and
.alpha.-(3-aminopropyl)-.omega.-(3-aminopropoxy)poly[oxy(1,4-butanediyl)]
with a molecular weight of from about 300 to about 3000.
Likewise suitable for reaction with phenylglyoxylic acid to form
the corresponding amides are monoamino polyols having only one
aliphatically bonded hydroxyl group, as described for component
d).
There are various options for incorporating structural units of
component c) having the formula I into the novel polyurethane. If
the compounds of component c) carry amino, thiol or aromatically
bonded carboxyl as functional group(s) then it is possible, for
example, to carry out addition onto isocyanate groups. This means
that component c) either is subjected to an addition reaction with
a prepolymer having free, terminal isocyanate groups or is present
in the reaction mixture as a reactive component during the
polyaddition reaction for preparing the polyurethane. Subsequent
addition reaction with a prepolymer having free isocyanate groups
can take place before, during or after the addition of water to the
isocyanato-containing prepolymer, to form urea, thiourethane or
amide linkages.
The same preconditions apply if one or more hydroxyl groups are
present on the photoinitiator as functional group(s). In this case,
an addition reaction with existing free isocyanate groups is
likewise carried out.
If the functional groups are isocyanate groups, then the compounds
of component c) can be reacted in the prepolymer synthesis together
with component a) with the other components b1), b2), d), e) or f)
which are required or desired for synthesizing the novel
polyurethane, in which case urethane groups are formed as a result,
for example, of reaction with hydroxyl groups from a polyol
component.
The addition reaction of the compounds of component c) which
contain isocyanate groups can also be carried out subsequently,
before, during or after the addition of water to the
isocyanato-containing prepolymer. By virtue of the further reaction
of the isocyanate groups with water or with an added diamine or
polyamine, the compounds of component c) are incorporated into the
polyurethane in a known manner by way of formation of urea
groups.
If the compounds of component c) contain aromatically bonded
hydroxyl groups as functional groups, then alkylene oxides, such as
ethylene oxide, propylene oxide or butylene oxide, are preferably
added onto the hydroxyl group prior to the reaction with isocyanate
groups. This addition reaction should in particular be allowed to
proceed to completion such that after the reaction there are no
aromatically bonded hydroxyl groups but only aliphatically bonded
hydroxyl groups left.
Prior to incorporation into the polyurethane and provided they have
hydroxyl groups, the compounds of component c) can be reacted with
polycarboxylic acids, phosgene, phosgene analogs or caprolactones
to form polyester-, polycarbonate- or polycaprolactonepolyols by
known methods and can be incorporated as such, by reaction with
free polyisocyanates, into the polyurethane.
Compounds of component c) which carry carboxyl groups as functional
groups can be used to prepare hydroxyl-containing polyesters by
known methods. This is generally accomplished by reaction with
polyols as have already been mentioned in the context of the
description of components b1) and b2).
If the compounds of component c) carry as functional groups a
2-oxa-1,3-bis(oxo)-1,3-propanediyl radical, then the structural
units of the formula I are preferably reacted with polyols in a
ring-opening monoesterification to form carboxyl-containing
polyols.
In overall terms, the hydroxyl-containing compounds of component c)
can be converted by a number of reactions known to the skilled
worker, for example esterification with carboxylic acids, reaction
with phosgene or with caprolactones, to form polyols having the
desired photoinitiator activity of component c). The polyols
prepared in this way can readily be reacted further to form the
novel polyurethanes by employing them, for example, in a mixture
with component b1) or with component b2) or even in place of one of
these components.
The photoinitiator-containing polyols described here can also be
used in a mixture with one another to prepare the novel
polyurethanes. These polyols have an average molecular weight of
from about 240 to about 5000, preferably from about 300 to about
2500 and, with particular preference, from about 1000 to about 2000
g/mol. The average functionality is from about 1 to about 5,
preferably from about 1.5 to about 3 and, with particular
preference, from about 1.8 to about 2.2.
The conditions for the reaction of the compounds of component c),
if they carry amino, mercapto and/or carboxyl and hydroxyl groups,
with free polyisocyanates or with prepolymers carrying free
isocyanates should be chosen such that the fully reacted
polyurethane contains no more than 10% of the amount employed of
amino groups, mercapto groups or hydroxyl and/or carboxyl groups
originating from this reaction.
If the compounds of component c) are reacted with an
isocyanato-containing polyurethane prepolymer it is also possible
to use compounds of higher functionality having three or four
functional groups, especially amino and/or mercapto groups, if the
reaction takes place during or after the dispersion of the
polyurethane prepolymer.
The concentration of compounds of component c), based on solid
resin, is from 20 to 2000, preferably from 50 to 1000 and, with
particular preference, from 100 to 500 mmol/kg.
If compounds of component c) carry at least one isocyanate-reactive
group and also at least one carboxyl or sulfo group which does not
serve for incorporation into the polyurethane, or if polyols
prepared using a corresponding compound of component c), as
described above, are used to prepare the novel polyurethanes, then
the resulting polyurethanes carry free carboxyl or sulfo groups. It
is therefore possible to introduce ionizable groups into the novel
polyurethane without the use of components e).
As component d) it is possible, for example, to employ chain
extenders or compounds having a functionality of more than two
which are suitable for introducing branching and which can also
have at least one primary or secondary amino group or else, insofar
as there is more than one amino group per molecule, primary and
secondary amino groups at the same time.
In addition to the amino groups the compounds of component d) can
also have further functional groups, especially isocyanate-reactive
groups. These include, in particular, hydroxyl groups or mercapto
groups.
Examples of the compounds which can be employed for the purposes of
the invention as component d) include monoamino polyols having an
aliphatically bonded hydroxyl group, such as ethanolamine,
N-methylethanolamine, N-ethylethanolamine, N-butylethanolamine,
N-cyclohexylethanolamine, N-tert-butylethanolamine, leucinol,
isoleucinol, valinol, prolinol, hydroxyethylaniline,
2-(hydroxymethyl)piperidine, 3-(hydroxymethyl)piperidine,
2-(2-hydroxymethyl)piperidine, 2-amino-2-phenylethanol,
norephedrine, 2-amino-1-phenylethanol, ephedrine,
p-hydroxyephedrine, adrenaline, noradrenaline, serine, isoserine,
phenylserine, 1,2-diphenyl-2-aminoethanol, 3-amino-1-propanol,
2-amino-1-propanol, 2-amino-2-methyl-1-propanol, isopropanolamine,
N-ethylisopropanolamine, 2-amino-3-phenylpropanol,
4-amino-1-butanol, 2-amino-1-butanol, 2-aminoisobutanol,
neopentanolamine, 2-amino-1-pentanol, 5-amino-1-pentanol,
2-ethyl-2-butyl-5-aminopentanol, 6-amino-1-hexanol,
2-amino-1-hexanol, 2-(2-aminoethoxy)ethanol,
3-(aminomethyl)-3,5,5-trimethyl-cyclohexanol, 2-aminobenzyl
alcohol, 3-aminobenzyl alcohol, 3-amino-5-methylbenzyl alcohol and
2-amino-3-methylbenzyl alcohol.
If the use of component d) is intended, for instance, to produce
chain branches, then it is possible, for example, to employ
monoamino polyols having two aliphatically bonded hydroxyl groups,
such as 1-amino-2,3-propanediol, 2-amino-1,3-propanediol,
2-amino-2-methyl-1,3-propanediol, 2-amino-2-ethyl- 1,3-propanediol,
2-amino-1-phenyl-1,3-propanediol, diethanolamine,
diisopropanolamine, 3-(2-hydroxyethylamino)propanol and
N-(3-hydroxypropyl)-3-hydroxy-2,2-dimethyl- 1-aminopropane.
Likewise possible is the use of polyamines as component d). These
include compounds such as, for example, hydrazine, ethylene
diamine, 1,2- and 1,3-propylenediamine, butylenediamines,
pentamethylenediamines, hexamethylenediamines, for example
1,6-hexamethylenediamine, alkylhexamethylenediamines, for example
2,4-dimethylhexamethylenediamine, generally alkylenediamines having
up to about 44 C atoms, where cyclic or polycyclic alkylenediamines
can also be employed as can be obtained, for example, in a known
manner from the dimerization products of unsaturated fatty acids.
It is likewise possible to employ aromatic diamines, for example
1,2-phenylenediamine, 1,3-phenylenediamine or 1,4-phenyldiamine.
Examples of higher amines which can be employed for the purposes of
the invention are diethylenetriamine, triethylenetetramine and
aminomethyl-1,8-diaminooctane.
In order to render the polyurethanes dispersible in water they
generally have incorporated into them hydrophilicizing, nonionic,
anionic or cationic structural units or structural units which can
be converted into anionic or cationic groups.
By structural units which can be converted into anionic or cationic
groups there are meant, for the purposes of the present invention,
those structural units which can be converted to an ionic form by a
simple chemical reaction, for example addition of base, addition of
acid or quaternization with, for example, alkyl halides. Examples
of such units are acid groups, tertiary amines or amides.
In addition to the components a), b1), b2), c) and, if used, d),
further hydrophilic components e) are incorporated during the
preparation of the novel polyurethanes insofar as dispersibility in
water has not already been provided by the incorporation of
suitable polyether chains as part of the incorporation of
components b1) and/or b2). Suitable components e) are compounds
having at least one isocyanate-reactive group and at least one
group which can be ionized by addition of base, addition of acid or
quaternization or has already been ionized by such a reaction. In
the text below the terms anionic groups and cationic groups are
used synonymously both for groups which have been ionized by
addition of acid or base or by quaternization and for the free
acids or free bases, unless specified otherwise.
The proportion of component e) with anionic or cationic groups in
the totality of components a), b1), b2), c) and, if used, d) is
generally such that the molar amount of the anionic or cationic
groups, based on the amount by weight of all of the components
employed, is from about 30 to 1000, preferably from about 50 to 600
and, with particular preference, from about 80 to 500 mmol/kg. In
any case, however, the proportion of component e) is high enough
for the resulting polyurethane to be at least substantially
self-dispersible in water.
Those compounds incorporated into the polyurethane as component e)
are in particular those which carry anionic groups such as the
sulfonate, the carboxylate or the phosphonate group or mixtures of
two or more thereof. This is effected either in the form of the
free acids or, preferably, in the form of their alkali metal salts
or ammonium salts, possible counterions being cations, such as
ammonium ions, especially protonated tertiary amino groups or
quaternary ammonium groups.
Potential ionic hydrophilic groups are, in particular, those which
can be converted into the abovementioned ionic hydrophilic groups
by means of simple neutralization, hydrolysis or quaternization
reactions, i.e. for example carboxyl, anhydride or amino groups,
the latter preferably being tertiary amino groups.
Suitable monomers having anionic groups are usually aliphatic,
cycloaliphatic, araliphatic or aromatic carboxylic or sulfonic
acids which carry at least one alcoholic hydroxyl or at least one
primary or secondary amino group. Preference is given to the
hydroxyalkylcarboxylic acids, especially those of 3 to 10 carbons,
described in U.S. Pat. No. 3,412,054. Particular preference is
given to dimethylolpropionic acid (DMPA).
Other compounds suitable as component e) are corresponding
dihydroxysulfonic acids and dihydroxyphosphonic acids or basic
phosphines, such as diethyl-.beta.-hydroxyethylphospline,
methyl-bis-.beta.-hydroxyethylphosphine and
tris-.beta.-hydroxymethylphosphine and also
bis(.alpha.-hydroxyisopropyl)phosphinic acid,
hydroxyalkanephosphinic acid and bis-glycol phosphate.
Compounds otherwise suitable are hydroxyl compounds having a
molecular weight of more than 500 to 10,000 g/mol and at least two
carboxylate groups, as are known, for example, from DE-A 3 911 827.
They are obtainable by reacting dihydroxy compounds with
tetracarboxylic dianhydrides, such as pyromellitic dianhydride or
cyclopentanetetracarboxylic dianhydride, in a polyaddition reaction
in a molar ratio of from 2:1 to 1.05:1. Particularly suitable
polyhydroxy compounds are the low molecular mass diols and polyols
listed under b1.2) and b1.3).
Compounds having tertiary amino groups are of particular practical
importance as component e) carrying cationic groups, examples being
tris(hydroxyalkyl)amines, N,N'-bis(alkyl)alkylamines,
N-hydroxyalkyldialkylamines, tris(aminoalkyl)amines,
N,N'-bis(aminoalkyl)alkylamines, N-aminoalkyldialkylamines, the
alkyl and the alkanediyl of these tertiary amines consisting
independently of one another of from one to six carbons. Also
suitable are polyethers having tertiary nitrogens and preferably
two terminal hydroxyls, as obtainable, for example, by conventional
alkoxylation of amines having two hydrogens attached to amine
nitrogen, for example methylamine, aniline or
N,N'-dimethylhydrazine. Polyethers of this kind generally have a
molar weight of from 500 to 6000 g/mol.
These tertiary amines are converted into the corresponding ammonium
salts either with acids, preferably strong mineral acids such as
phosphoric acid, sulfuric acid or hydrohalic acids, or with strong
organic acids, for example formic acid or acetic acid, or by
reaction with suitable quaternizing agents, such as C.sub.1-6
-alkyl halides, for example alkyl bromides or alkyl chlorides, or
benzyl halides.
The compounds employed as component e) can be converted into their
ionic form before, during or--preferably--after the isocyanate
polyaddition reaction, since the ionic monomers are frequently of
poor solubility in the reaction mixture.
As component f) for preparing the novel polyurethane it is possible
if desired to employ compounds having at least one
isocyanate-reactive group and at least one olefinically unsaturated
double bond. The olefinically unsaturated double bond preferably
lends itself readily to free-radical polymerization, and with
particular preference is a double bond activated by aromatic groups
or by carbonyl groups as is present, for example, in styrene or in
acrylic acid, methacrylic acid or esters thereof.
In the text below, when referring to acrylic acid or methacrylic
acid or derivatives thereof, the form (meth)acrylic acid is used,
as for example in poly(meth)acrylic acid.
Where compounds having only one isocyanate-reactive group are
employed as component f) the olefinically unsaturated double bonds
are incorporated at the end of the polyurethane chain. Where
compounds having two or more isocyanate-reactive groups and at
least one olefinically unsaturated double bond are used as
component f) incorporation generally takes place, given an
appropriate reaction regime, in the polyurethane chain, although
incorporation at the chain end is possible in this case too.
Incorporation in the polyurethane chain refers for the purposes of
the invention both to incorporation of the double bond as part of
the polymer backbone and to introduction of the double bond in the
form of a side chain. Examples of suitable monomers containing
hydroxyl groups and at least one olefinically unsaturated double
bond are hydroxyalkyl (meth)acrylates, such as 2-hydroxyethyl
(meth)acrylate, hydroxypropyl(meth)acrylates and 4-hydroxybutyl
(meth)acrylate. Polypropylene glycol mono(meth)acrylates and
polyethylene glycol mono(meth)acrylates are also suitable.
Compounds suitable for introducing two or more olefinically
unsaturated double bonds are the poly(meth)acrylates of polyhydric
alcohols, such as glycerol di(meth)acrylate, trimethylolpropane
di(meth)acrylate, and pentaerythritol di- or tri(meth)acrylate.
Using appropriate polyol components having at least two hydroxyl
groups, the olefinically unsaturated double bonds can be
incorporated not only at the end of the polyurethane chain but also
as a side chain on the polymer backbone. Compounds suitable for
this purpose are, for example, glycerol mono(meth)acrylate,
trimethylolpropane mono(meth)acrylate and pentaerythritol mono- or
-di(meth)acrylate. Likewise suitable for use for this purpose are
the ring opening products of (meth)acrylic acid with bisepoxides,
for example the glycidyl ethers of bisphenol A, ethylene glycol,
1,4-butanediol or 1,6-hexanediol.
If desired it is also possible as component f) to employ oligomeric
or polymeric compounds which carry at least one isocyanate-reactive
group and at least one olefinically unsaturated double bond.
Examples of these include polyesters which have been prepared with
the aid of olefinically unsaturated diols or polyols or,
preferably, with the aid of olefinically unsaturated dicarboxylic
acids or polycarboxylic acids. Preference is given to the use of
those polyesters which can be prepared using the components
described for b1.1) and b1.2) with the at least partial use of
unsaturated dicarboxylic acids, for example maleic acid, maleic
anhydride or fumaric acid.
The acid groups present in the novel polyurethane are neutralized
prior to or, preferably, after incorporation into the polyurethane
chain, using a basic neutralizing agent. Suitable basic
neutralizing agents are, in general, for example alkali metals,
such as Li, Na or K, and the alkaline earth metals, such as Ca, Mg,
Ba or Sr, although the latter are not preferred in the context of
the present invention. More suitable, and preferred in the context
of the present invention, are all salts of the abovementioned
metals that are capable of reacting to neutralize the acid groups,
especially the carbonates or the hydroxides, for example LiOH,
NaOH, KOH or Ca(OH).sub.2. Of the latter, NaOH is particularly
preferred.
Also suitable for neutralization and particularly preferred in the
context of the present invention are organic, nitrogen-containing
bases, for example ammonia, and amines, such as trimethylamine,
triethylamine, tributylamine, dimethylaniline,
dimethylethanolamine, methyldiethanolamine or triethanolamine, and
mixtures thereof. Neutralization with the nitrogen-containing
organic bases can be carried out in the organic or in the aqueous
phase. Compounds of component e) neutralized with
nitrogen-containing bases, as described below, are therefore
generally also suitable in neutralized form for incorporation into
the polyurethane in organic solution.
If neutralization of the acid groups is desired, the neutralizing
agent can be added in an amount such that a sufficient proportion
of the acid groups, generally from about 0.1 to 100%, is
neutralized.
In general at least 10%, preferably 25% and, with particular
preference, at least 50% of the ionizable groups present in the
novel polyurethane that can be converted to anionic or cationic
groups by addition of acid or base or by quaternization are
neutralized. However, it is also possible for at least 75% or, for
example, even substantially all--i.e. about 100%--of the ionizable
groups, present in the novel polyurethane, to be neutralized.
The novel polyurethane should preferably be non-crystalline and
non-semicrystalline and should have a number-average molecular
weight (M.sub.n) of at least 2700 and/or a weight-average molecular
weight (M.sub.w) of about 5000 g/mol. The required lower limit of
the molecular weight is dependent on the desired morphology of the
coating which is obtainable by physical drying. In general, the
lower limit should be chosen such that optically flawless surfaces
which are tack-free, dust-dry or solid even before UV irradiation
are formed from the novel coating composition. Depending on the
structure of the polyurethane this can be ensured even at molecular
weights upward of about 2700 (M.sub.n), although higher lower
limits may also be desirable for the molecular weight M.sub.n, for
example 3000, 4000, 5000 or even 8000 to 10,000 daltons. The upper
limit is determined largely by the upper limit which can be
achieved by the particular synthesis process employed. Further
limiting factors are, for example, the solution viscosity of the
polyurethane and the processing properties and crosslinking
properties of the resulting coating composition. In general an
upper limit of about 100,000 daltons for M.sub.n is sufficient,
although the molecular weight can also be lower, for example 50,000
or 30,000 daltons.
In this context the molecular weight can be determined by methods
familar to the skilled worker, for example membrane osmometry,
vapor pressure osmometry, gel permeation chromatography,
time-of-flight mass spectrometry, viscometry or light
scattering.
The invention additionally relates to a process for preparing the
novel polyurethane, as described above, in which polyisocyanates of
component a) are reacted at least with one or more polyols of
component b) and with at least one compound of component c) and
also, if desired, with one of components d), e) or f) or with a
mixture of two or more thereof.
The invention additionally provides an aqueous polyurethane
dispersion which comprises at least one of the above-described
polyurethanes which are essentially self-dispersible in water and
are prepared from components a), b) and c) and, if desired, d), e)
or f) or from a mixture of two or more thereof. If the
polyurethanes have been prepared using component f) they contain at
least one olefinically unsaturated double bond in the polymer
chain. Polyurethane dispersions of this kind are crosslinkable by
irradiation with UV light after drying, i.e. after at least
substantial removal of water and of any organic solvents
present.
If the novel polyurethanes have been prepared without compounds of
component f) then the novel polyurethane dispersions are blended
with a further component comprising compounds having free-radically
polymerizable, olefinically unsaturated double bonds. Such blending
can also be undertaken, however, even if the novel polyurethane
employed contains olefinically unsaturated double bonds.
Appropriate olefinically unsaturated double bonds are, in
particular, olefinic double bonds from .alpha.,.beta.-unsaturated
ester compounds, for example the esters of acrylic acid or of
methacrylic acid. These compounds containing unsaturated ester
groups can be mixed, in solid, liquid or solution form (in organic
solvents) or as a dispersion or emulsion of a compound containing
chemically bonded, unsaturated ester groups, with the novel
polyurethane prior to or after dispersion in water.
The compound containing unsaturated ester groups is preferably a
polymer or a mixture of two or more polymers, it being possible for
the polymer or polymers to be polyadducts, polycondensates or
polymers prepared by a free-radical method. The chemical attachment
of the unsaturated groups can be accomplished by copolymerizing a
monomer having one or more unsaturated ester groups or, especially
in the case of a polymer prepared by free-radical polymerization,
by means of a subsequent, polymer-analogous reaction. This
polymer-analogous reaction can take place either in organic
solution before addition to the novel dispersion or in the novel
dispersion itself.
It is preferred to employ polymers containing olefinically
unsaturated double bonds. These include, for example, polyesters as
obtainable by reaction of polyols, as have been described, for
example, under b1.2) and b1.3), with dibasic to tetrabasic
carboxylic acids, described for example under b1.1), and, for
example, (meth)acrylic acid.
The polymers which contain olefinically unsaturated double bonds
and which are introduced into the dispersion if desired in addition
to the novel polyurethane generally have a molecular weight of at
least about 300, preferably at least about 400. These polymers
preferably have no urethane groups.
The content of unsaturated ester groups, based on the dry mass of
the dispersion, preferably based on the dry mass of the polymeric
binders, is from about 50 to about 2500, preferably from about 100
to about 2000 and, with particular preference, from about 150 to
about 1500 mmol/kg.
The term polymeric binders which is used to define the
concentration of compounds of component c) and of olefinically
unsaturated double bonds relates exclusively to the novel
polyurethane in the case where the novel polyurethane contains such
olefinically unsaturated double bonds and there is no longer any
other polymer containing olefinically unsaturated double bonds
present in the novel dispersion. In the case where the novel
polyurethane does not have olefinically unsaturated double bonds
and where there is a further, polymeric binder component which has
olefinically unsaturated double bonds present in the novel
dispersion alongside the novel polyurethane, the term solid resin
refers to the overall amount of polymeric binder, comprising novel
polyurethane and further polymeric binders containing olefinically
unsaturated double bonds. The same applies if further polymeric
binders containing olefinically unsaturated double bonds are
employed in addition to the novel polyurethane containing
olefinically unsaturated double bonds.
The proportion of water in the novel dispersions or emulsions is
from about 20 to about 80% by weight, preferably from about 25 to
about 75% by weight and, with particular preference, from about 30
to about 65% by weight.
The proportion of polyurethane, based on the overall solid resin,
is at least about 20% by weight, preferably at least about 40% by
weight and, with particular preference, at least about 60% by
weight.
The invention additionally relates to a process for preparing an
aqueous polyurethane dispersion, in which at least one novel
polyurethane, alone or together with further polymeric binders and
further customary coatings additives, is dissolved or dispersed in
water.
The invention also provides a coating composition obtainable by
dissolving or dispersing in water at least one novel polyurethane,
alone or together with further polymeric binders and further
customary coatings additives.
The invention likewise provides a process for preparing a coating
composition, in which at least one novel polyurethane, alone or
together with further polymeric binders and further customary
coatings additives, is dissolved or dispersed in water.
The coating composition prepared in accordance with the invention
also contains further customary coatings additives. These include,
in particular, thickeners, pigments, organic solvents in
proportions of not more than 20%, dyes, emulsifiers, surfactants,
heat stabilizers, leveling assistants, wetting agents, fillers,
sedimentation inhibitors, flame retardants or antioxidants or
mixtures of two ore more thereof, which can be added simultaneously
or in succession at any desired point in time during the
preparation of the coating composition.
The novel coating compositions can be applied to a large number of
substrates, for example to wood, metal, glass, fabric, leather,
concrete, paper, plastic, plastic foam and the like.
The present invention therefore likewise provides a process for
coating articles with the novel polyurethane dispersions or coating
compositions, in which the novel polyurethane dispersions or
coating compositions are applied to the article by means of a
technique customary in coatings technology, such as rolling,
spreading, knife coating, spraying, dipping or another technique,
are first of all dried and then are crosslinked by irradiation with
UV rays.
The invention also provides articles coated, preferably by the
above process, with one of the novel polyurethane dispersions or
coating compositions.
EXAMPLES
Abbreviations
______________________________________ DETA Diethylenetriamine DMEA
Dimethylethanolamine DMPA Dimethylolpropionic acid IPDI Isophorone
diisocyanate MEK Methyl ethyl ketone MW Molar weight TMP
Trimethylolpropane p parts
______________________________________
The following photoinitiators were incorporated in accordance with
the invention into the polyurethanes described:
A. Photoinitiator I: IRGACURE 500 (from CIBA-GEIGY)=1:1 mixture of
benzophenone and 1-hydroxycyclohexyl phenyl ketone
B. Incorporable photoinitiator II: Benzophenonetetracarboxylic
dianhydride
C. Incorporable photoinitiator III: IRGACURE 2959 (from
CIBA-GEIGY)
D. Incorporable photoinitiator IV: Phenylglyoxylic acid
E. Incorporable photoinitiator V:
F. Incorporable photoinitiator VI: ##STR5## Preparation
Instructions for Photoinitiator V
A mixture of 161.2 p (1 mol) of
N-(3-hydroxy-3,2-dimethylpropyl)-N-(3-hydroxypropyl)amine and 180 g
(1.1 mol) of methyl phenylglyoxylate was reacted at 80.degree. C.
for 4 hours under a reduced pressure of 30 mbar. During this time,
33.4 p (1.045 mol) of methanol were eliminated. The product was a
viscous, pale brownish mass. .sup.1 H-NMR confirmed the desired
structure in the product mixture to the extent of at least 90%. The
hydroxyl number was 350 mg of KOH/g (theory 365).
Preparation Instructions for Photoinitiator VI
75.1 p (0.46 mol) of methyl phenylglyoxylate and 300 p of ethanol
were introduced into a vessel. 57 p (0.45 mol) of
N-3-aminopropylimidazole were added. After stirring at room
temperature for 2 hours, the solvent was removed. The product was a
viscous, almost colorless mass. .sup.1 H-NMR analysis indicated a
purity of at least 95%.
Dispersion 1
400 p (0.4 mol) of polyesterdiol (based on adipic acid, isophthalic
acid and 1,6-hexanediol and having a MW of 1000) were reacted with
51.6 p of photoinitiator II (0.16 mol) at 125.degree. C. until the
mixture became clear. 148.7 p of 1,4-butanediol (1.65 mol) and 300
g of MEK were added. After cooling to 70.degree. C., 453.5 p of
IPDI (2.04 mol) were added. After a further 3.5 hours the mixture
was diluted with 600 p of acetone, the isocyanate content being
0.9% by weight (theory 0.64%). The reactor was protected against
light, and 362.3 p of acrylate resin LAROMER.RTM.LR 8945 were
added. For neutralization, 22.82 p (0.256 mol) of
dimethylethanolanine were added (theoretical degree of
neutralization 80%). Following the addition of 2000 p of water and
10.3 p (0.1 mol) of DETA, the acetone was removed by distillation.
Solids content: 43.7%, pH 7.2.
Dispersion 2
400 p (0.4 mol) of polyester (as in Example 1), 169.8 p (0.8 mol)
of photoinitiator III, 40.2 p (0.3 mol) of DMPA, 36 p of
1,4butanediol (0.4 mol) and 250 p of MEK were introduced into a
vessel. Following the addition of 452.4 p (2.04 mol) of IPDI, the
mixture was reacted at 80.degree. C. After one hour 33.6 p (0.25
mol) of TMP were added. After 3 hours the mixture was diluted with
500 g of acetone, the isocyanate content being 0.69% by weight
(theory 0.71%). After neutralization with 24 p of 50% strength
NaOH, addition of 1950 g of water and crosslinking with 8.8 g (0.09
mol) of DETA an opaque dispersion was formed. Solids content:
35.8%, pH 9.7.
Dispersion 3
Dispersion 3 was prepared in a manner similar to that used for
dispersion 2 with the difference that only 84.9 p (0.4 mol) of
photoinitiator III but an additional 46.4 p (0.4 mol) of
hydroxyethyl acrylate were used. The reactor was protected against
light. An opaque dispersion was formed. Solids content: 37.7%, pH
8.5.
Dispersion 4
200 p (0.1 mol) of polyesterdiol (based on adipic acid, isophthalic
acid and 1,6-hexanediol, MW 2000), 44.94 p (0.34 mol) of DMPA, 48.1
p (0.78 mol) of ethylene glycol, 275 p of MEK and 21.22 p (0.1 mol)
of photoinitiator III and 241.2 p (1.38 mol) of an isomer mixture
of 80% 2,4- and 20% 2,6-tolylene diisocyanate were reacted at
90.degree. C. After one hour 6.71 p (0.05 mol) of TMP and, after a
further 3 hours, 99 p of LAROMER.RTM.LR 8945 were added. After an
additional 2 hours, at 90.degree. C., 275 p of acetone, 26.8 p of
50% strength NaOH and 1100 p of water were added in succession. The
acetone was removed by distillation. A pale brownish and
translucent dispersion was formed. Solids content 36.6%, pH
8.0.
Dispersion 5
Dispersion 5 was prepared by a method similar to that used for
dispersion 2 with the difference that the photoinitiator III was
replaced by 120.1 p (0.8 mol) of photoinitiator IV, photoinitiator
IV and IPDI having been reacted with one another at 90.degree. C.
for 2.5 hours beforehand without any other components. Following
dilution with acetone the isocyanate content was 0.46%. A pale
yellowish, opaque dispersion was formed. Solids content 34% by
weight, pH 7.6.
Dispersion 6
200 p (0.1 mol) of polyesterdiol as in dispersion 4 (based on
adipic acid, isophthalic acid and 1,6-hexanediol, MW 2000), 45 p
(0.36 mol) of DMPA, 46.1 p (0.74 mol) of ethylene glycol, 275 p of
MEK and 30.5 p (0.1 mol) of photoinitiator V were reacted with
231.9 p (1.33 mol) of an isomer mixture comprising 80% 2,4- and 20%
2,6-tolylene diisocyanate at 90.degree. C. for 4 hours. Then 99 p
of LAROMER.RTM.LR 8945 were added and the mixture was reacted, with
protection from light, at 90.degree. C. for 2 hours. Subsequently
275 p of acetone, 26.8 p of 50% strength NaOH and 1100 p of water
were added in succession. The acetone was removed by distillation.
A brownish translucent dispersion was formed. Solids content
38.6%.
Dispersion 7
200 p of polyesterdiol as in dispersion 4 (0.1 mol), 20.1 p of DMPA
(0.15 mol), 26.1 p of 1,4-butanediol (0.29 mol), 22.0 p of
photoinitiator V (0.075 mol) and 200 p of MEK were introduced into
a vessel. 82.7 p of TDI (0.475 mol) were added, and the mixture was
reacted at 80.degree. C. for 2 hours. Then 45.0 p (0.203 mol) of
IPDI were added and the mixture was reacted at 80.degree. C. for 2
hours. Then 12.9 p (0.05 mol) of photoinitiator VI were added and
the mixture was reacted at 75.degree. C. for 6 hours.
It was then diluted with 300 p of acetone, neutralized with 8.0 p
(0.09 mol) of DMEA and dispersed with 1000 p of deionized water.
The acetone was distilled off. Solids content: 29.4%, pH 7.4.
Dispersion 8
Dispersion 8 was prepared as for dispersion 7 with the difference
that photoinitiator VI was not added. Solids content: 32.6%, pH
6.5.
Dispersion 9
200 p of polyesterdiol (based on adipic acid, ethylene glycol;
MW=2000) (0.1 mol), 32.2 p (0.24 mol) of DMPA, 29.3 p (0.325 mol)
of 1,4-butanediol and 90 p of MEK were introduced into a vessel.
180.1 p (0.18 mol) of IPDI were added and the mixture was reacted
at 90.degree. C. for about 2.5 hours. Following the addition of 6.7
p (0.05 mol) of TMP the mixture was left to react at 90.degree. C.
for one hour more. Then 36.0 p (0.14 mol) of photoinitiator VI were
added, and the mixture was reacted for 3 hours more. Then 350 p of
acetone and 17.1 p (0.192 mol) of DMEA and 1100 p of deionized
water were added. The acetone was distilled off. Solids content:
29.0%, pH 7.5.
Comparison Dispersion 1
Comparison dispersion 1 was prepared as for dispersion 2 with the
difference that photoinitiator III was replaced by 92.9 p (0.8 mol)
of hydroxyethyl acrylate. An opaque dispersion was formed. Solids
content: 38.2%, pH 8.5.
Comparison Dispersion 2
LAROMER.RTM. 8949, a commercially available polyurethane dispersion
with incorporated acrylic ester groups from BASF AG.
Film Preparation
A film of the above dispersions was applied to a glass plate using
a 200 .mu.m doctor blade. The film was dried at room temperature
for about 5 to 10 minutes. The film was subsequently treated at
60.degree. C. in a drying oven for 20 minutes.
Pendulum Hardness
The pendulum hardness was determined in accordance with DIN 53 157
using a Konig instrument. The time in seconds was determined.
Chemical Resistance
The chemical resistance test was carried out in accordance with DIN
68 861. However, only 10 test media were selected from the entire
range, and exposure group 1b was configured accordingly. The
individual test media are sodium carbonate, red wine, instant
coffee, blackcurrant juice, ethylbutyl acetate, mustard, lipstick,
disinfectant, ballpoint pen paste and cleaning fluid.
Spray Application
Application was carried out with a flow cup gun with nozzles of 1.3
to 1.6 mm. The pressure of the gun inlet was from about 2 to 2.5
bar. In the case of application to wood, two coats of about 100
p/m.sup.2 were applied in each case. Between the first and the
second coat, the film was dried at 60.degree. C. for 15 minutes and
then exposed to UV at a rate of 5 m/min. Before applying the second
coat, sanding was carried out (coarseness about 240). The second
layer was dried and exposed as for the first.
__________________________________________________________________________
Test results Ex. 1 2 3 4 5 6
__________________________________________________________________________
Coating test method Disp. 1 100 p Disp. 3 50 p 100 p 100 p Disp. 2
+ Disp. 5 + comp. comp. 100 p 100 p disp. 2 + disp. 1 + comp. comp.
3 p 3 p disp. 2 disp. 2 Photoinit. I Photoinit. I Pendulum hardness
40 76 55 46 7 39 before UV Pendulum hardness 70 86 108 75 147 106
after UV Chemical resistance 3 2.55 2.85 2.65 3.3 2.75 before
UV.sup.1) Chemical resistance 1.3 0.85 1.05 0.95 0.8 1.15 after
UV.sup.1) Odor - - - - + +
__________________________________________________________________________
.sup.1) 0 = best value
All dispersions with covalently incorporated photoinitiator showed
a marked improvement in film resistance after UV irradiation
coupled with outstanding physical drying.
In the case of Examples 5 and 6, a slight odor of benzaldehyde was
noted following irradiation.
Comparison of Example 2 with Example 4 shows that the covalently
incorporated photoinitiator is just as effective as a corresponding
added photoinitiator. An identical result is shown by comparing
Example 3 with Example 5 as well.
* * * * *